I understand there are many people who desire a faithful recreation of the game, but I don’t know if that’s enough for people who haven’t been playing D2 for 20 years. My most desired QoL features are hotbars, and gem stacking and/or stash space.
Memorizing which function keys rebind which skills to which mouse button is more mechanical and mental effort than I’d like. The inclusion of hotbars for controllers means that for me, controller would be the preferred control method. That being said, I’d rather have hotbars on my keyboard, with a corresponding UI to help me remember what the binds are. I don’t think hotbars should be the default, but an option to be enabled in the settings.
The only problem with the controller layout I’ve had is having the A button as the default interact button while also being the default attack button. This means when in combat, you might suddenly be trying to stuff items into your bag rather than attacking. Those default functions of the A button (picking up items, opening doors and chests) shouldn’t be able to be bound to the same key as any other functions. The option exists to bind them, but does not disable A from being the default interact.
It seems like perhaps hotbar space was an issue, with only 2 hotbars being available. I would suggest a base layer with 6 slots for the face buttons and bumpers, and the d-pad for potions, with the ability to use LT, RT, and even LT+RT as modifiers to access 3 more layers of 10 functions each corresponding to the buttons and d-pad. Now that I write that, I’m not sure anyone would need that many slots, but something akin to that layout would work well. Then again, ability to use the right stick to aim abilities would also make kiting and maneuvering in combat a more enjoyable affair, but that would require skills bound to the triggers and bumpers. So perhaps a similar concept as above, but using a face button to open a radial wheel to select an action layer with binds for d-pad, remaining face buttons, bumpers and triggers.
After Act I with a single class my shared stash was half full of gems. I honestly don’t know much about D2 endgame, but have read a lot on the value of stacking gems, in addition to concerns of how it would affect the trading economy. As a predominantly solo self-found player, with a strong tendency towards hoarding, some combination of gem stacking, better gem storage, or more space would be appreciated. However I do realize you want to keep character file sizes smaller to support ease server loads, especially with cross progression as a feature.